Lung mechanics 2

Question 1

How to collect data for static presure-volume loop

Answer 1

intrapleural pressure measured with oesophageal balloon, volume measured with spirometer. Breathe in from RV to TLC

Question 2

Draw static pressure-volume loop and comment

Answer 2

Maximum volume change for transmural pressure at TV gradient increase here, Compliance minimum at low and high volumes. Volume of lung for expiration always larger for same distending pressure

Question 3

Lung compliance pathology examples

Answer 3

Low compliance-lung fibrosis (dense honeycomb appearance, Neonatal respiratory distress syndrome (deficient surfactant)
High compliance-emphysema
No effect=asthma

Question 4

LaPlace equation

Answer 4

Pressure =2T/radius surface tension must be overcome to stretch air-fluid interface

Question 5

If 2 bubbles had the same tension but different radii, how would its pressure differ?

Answer 5

Smaller radius higher pressure

Question 6

What is surfactant, where is it made and what does it do?

Answer 6

What-mixture of phospholipids and surfctant proteins
where-type II alveolar cells
function-float on surface of alveolar lining fluid and reduces surface tension in proportion to surface concentration

Question 7

How surfactant affects surface tension as alveolous shrinks

Answer 7

surface concentration of surfactant rises so T falls. Even though radius decreases, tension falls more. This means P falls

Question 8

Effect of surfactant

Answer 8

Increases compliance
Reduces tendency for alveoli to collapse
reduces tendency to suck fluid into alveoli

Question 9

Neonatal respiratory distress syndrome

Answer 9

Inadequate surfactant production in premature babies. Increased work of breathing due to reduced compliance and lung collapse

Question 10

Obstructive lung disease example

Answer 10

Airflow impeded
asthma: airways narrowed, alveoli normal
chronic bronchitis: airways damaged hypertrophied glands and mucus production, alveoli normal (COPD)
emphysema: airways poorly supported, alveoli destroyed, muscles normal (COPD))

Question 11

Restrictive lung disease example

Answer 11

Poor lung expansion
Lung fibrosis: airways normal, alveoli stiff, fibrosis scar tissue, respiratory muscles normal
respiratory muscle weakness: everything normal but respiratory muscles weak

Question 12

How to measure airway resistance

Answer 12

Peak flow/forced expiratory volume vs time. Both tests involves breathing to total lung capacity and breathing out as hard and fast as posssible

Question 13

How to use and plot data from forced expiratory volume vs tim

Answer 13

FEV1=forced expiratory volume in 1 sec, FVC=forced vital capacity. Normally FEV1/FVC (forced expiratory ratio)>75%

Question 14

What happens to FEV1, FVC and forced expiratory ratio in healthy, obsttructive and restrictive

Answer 14

Healthy=all normal
Obstructive=FEV1 decrease a lot, FVC decrease a bit, overall ratio decreases. Can’t breathe out everything breathed in because airway collapses
Restrictive=FEV1 and FVC decreases by similar amounts so ratio is normal. Low vital capacity but airway is fine

Question 15

How do max flow-volume loop differ between Normal, obstructive and restrictive

Answer 15

Obstructive-concave appearance of forced expiratory curve, forced inspiratory flow less affected
Restrictive=low peak flow rates related to low volumee

Question 16

Effect on FRC for lung fibrosis and emphysema

Answer 16

lung fibrosis=reduce, emphysema=increase, barrel chest